2000 1.8TQM with 187,000 miles. I've had many P0411 codes over the years, and have been able to correct them by replacing elbows on the output lines up top, and also duct taping the cheap flex line that runs from the Pump output to the metal tubing. But, now I'll get a P0411 every couple of weeks or month while I'm driving. I understand why the
SAI pump should throw a code at start up (I can hear mine singing at cold starts), but why would this system indicate a failure at normal operating temps, and intermittently? It shouldn't even be running at operating temp (I think). I carry a parts store vag com cheap device in the glove box and reset it when it lights the CEL. Ideas? Thanks

 

How loud is your pump when it comes on at idle? It's possible that it's finally just not pushing enough air to satisfy the ECU checking on it. Mine is exactly the same way.

It's not that the pump is running when it shouldn't be, it just takes a few cycles of checking and re-checking measurements for the ECU to decide that there's something wrong with it. Depending on the mileage, that may or may not happen when the car is already up to operating temp